96 lines
2.1 KiB
C
96 lines
2.1 KiB
C
/*
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* Copyright (c) 2018 Aurelien Jarno
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*
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* SPDX-License-Identifier: Apache-2.0
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*/
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#include <device.h>
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#include <drivers/entropy.h>
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#include <errno.h>
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#include <init.h>
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#include <soc.h>
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#include <string.h>
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struct trng_sam_dev_cfg {
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Trng *regs;
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};
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#define DEV_CFG(dev) \
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((const struct trng_sam_dev_cfg *const)(dev)->config->config_info)
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static int entropy_sam_wait_ready(Trng *const trng)
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{
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/* According to the reference manual, the generator provides
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* one 32-bit random value every 84 peripheral clock cycles.
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* MCK may not be smaller than HCLK/4, so it should not take
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* more than 336 HCLK ticks. Assuming the CPU can do 1
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* instruction per HCLK the number of times to loop before
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* the TRNG is ready is less than 1000. And that is when
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* assuming the loop only takes 1 instruction. So looping a
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* million times should be more than enough.
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*/
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int timeout = 1000000;
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while (!(trng->TRNG_ISR & TRNG_ISR_DATRDY)) {
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if (timeout-- == 0) {
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return -ETIMEDOUT;
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}
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k_yield();
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}
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return 0;
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}
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static int entropy_sam_get_entropy(struct device *dev, u8_t *buffer,
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u16_t length)
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{
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Trng *const trng = DEV_CFG(dev)->regs;
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while (length > 0) {
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size_t to_copy;
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u32_t value;
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int res;
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res = entropy_sam_wait_ready(trng);
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if (res < 0) {
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return res;
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}
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value = trng->TRNG_ODATA;
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to_copy = MIN(length, sizeof(value));
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memcpy(buffer, &value, to_copy);
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buffer += to_copy;
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length -= to_copy;
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}
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return 0;
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}
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static int entropy_sam_init(struct device *dev)
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{
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Trng *const trng = DEV_CFG(dev)->regs;
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/* Enable the user interface clock */
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soc_pmc_peripheral_enable(DT_ENTROPY_SAM_TRNG_PERIPHERAL_ID);
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/* Enable the TRNG */
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trng->TRNG_CR = TRNG_CR_KEY_PASSWD | TRNG_CR_ENABLE;
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return 0;
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}
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static const struct entropy_driver_api entropy_sam_api = {
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.get_entropy = entropy_sam_get_entropy
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};
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static const struct trng_sam_dev_cfg trng_sam_cfg = {
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.regs = (Trng *)DT_ENTROPY_SAM_TRNG_BASE_ADDRESS,
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};
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DEVICE_AND_API_INIT(entropy_sam, CONFIG_ENTROPY_NAME,
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entropy_sam_init, NULL, &trng_sam_cfg,
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PRE_KERNEL_1, CONFIG_KERNEL_INIT_PRIORITY_DEVICE,
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&entropy_sam_api);
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